headband kit for sleep EEG? / longterm EEG techniques
@wjcroft Hi! Does the headband kit come with special instructions for keeping it clean and hygienic for wearers as well as for maintaining the contact/conduction quality of the flat ear electrodes, flat snap electrodes and spikey/comb electrodes? Or is this simply a matter of using replacement electrodes for old, worn and dirty electrodes?
Additionally, how about cleaning of the Velcro headband which would be in constant contact with the hair and skin of various users?
Comments
Scipio, hi.
So you are intending to use the headband kit with your 12 hour hospital study? Generally the dry silver chloride EEG electrodes used in that kit (and the Ultracortex headset) -- produce lower microvolts signals than you would get with electrodes using paste or gel. It's not a huge reduction, but it is common to see. Most EEG sleep studies use paste or gel electrodes and a cover layer (called collodion) to keep the electrolyte from evaporating. These are applied by EEG techs proficient in this technique.
The reason that wet gel elastic caps are not used long term, is again, that the electrolyte evaporates over many hours. Caps can work for say an hour, but after that your gel will start drying and affect signal quality.
The dry EEG electrodes are plastic based, with layers of silver, then chloride. So they cannot in general be subject to hospital sterilization techniques using heat or strong solutions. They could be cleaned with mild water / detergent solution; some disinfectants are not too harsh.
Hospital procedures can differ; you should check with the clinic you are working with.
The velcro band is a cloth / plastic mix, and could be cleaned.
https://www.google.com/search?as_q=collodion&as_sitesearch=openbci.com
https://www.google.com/search?q=eeg+collodion
https://www.spisop.org/openbci/
He mentions:
You may want to contact the author, it's possible that this Grass cream would last through the night without needing collodion.
@Frederik_D_Weber, can you confirm that your SPISOP overnight recordings worked fine with the Grass paste you mentioned? No collodion needed, etc. Any estimate of longest time period the EC2 would be good for? 12 hours?
Thanks, William
Found this paper, which says the EC2 is BETTER than conventional / older practice with the collodion,
https://www.ncbi.nlm.nih.gov/pubmed/15982926
Grass was founded by Albert Grass in 1935, and was a giant in the early medical EEG equipment industry. (One of my biomed professors in the 1970's was proud of his Grass EEG amplifier / recorder. Their stuff was considered the highest grade EEG gear.) Here's what the Wayback Machine has archived,
https://web.archive.org/web/*/grasstechnologies.com
https://web.archive.org/web/20160311030240/http://www.grasstechnologies.com/
https://web.archive.org/web/20160310222133/http://www.grasstechnologies.com/products/electrodes/electapplication.html
[pdf below shows EC2 as substitute for collodion]
It looks like Grass finally got absorbed in 2013 by Natus. I cannot find any evidence of the EC2 or EC3 creams being available online. Natus now sells the rather conventional Ten20 paste. If this is the case, looks like a sad loss for the PSG field.
https://astronovainc.com/natus-to-acquire-grass-technologies-product-group-from-astro-med/
https://www.natusneurostore.com/c-366-eeg-supplies-starter-kits.aspx
OK, my mistake, Natus still sells the EC3 in packs of 12 for $88. So someone doing PSG (sleep studies) may want to coordinate a group buy.
https://www.natusneurostore.com/p-1559-ec3-grass-conductive-adhesive-gel-176-oz-50-g-12pkg.aspx
@wjcroft Thanks for the update with the following link: https://www.natusneurostore.com/p-1559-ec3-grass-conductive-adhesive-gel-176-oz-50-g-12pkg.aspx. You write: "Generally the dry silver chloride EEG electrodes used in that kit (and the Ultracortex headset) -- produce lower microvolts signals than you would get with electrodes using paste or gel. It's not a huge reduction, but it is common to see."
We ought to have a dry solution for this at OpenBCI with the introduction of the headband kit (and Ultracortex headset).
Would not the interposition of a high quality noise-cancelling amplifier between the leads from the headband and the Cyton Daisy board do the trick by raising the microvolt signals? This would do away with the need for potentially messy 'Grass EC3 Electrode Cream' and keep the whole apparatus dry. However, in the absence of the amplifier, I may have just have to settle for the EC3 Gass Conductive Adhesive Gel.
Are you measuring EEG during sleep? If so, dry electrodes will produce spurious readings because of pressure changes as the head rolls around. With an electrolyte layer between the skin and electrode, such variations are minimized. PSG studies have used conventional electrodes for decades.
There are no "noise cancelling amplifiers" currently available for OpenBCI. The technical term is "active electrode". And high end EEG systems offer this.
Your best bet for sleep electrodes may be disposable silver chloride with the EC3 paste. This way no cleaning or hygiene requirements are required.
https://www.google.com/search?q=disposible+eeg+electrodes+silver+chloride
@wjcroft Yes, I would be measuring EEG both in the state of wakefulness and sleep. The electrodes in the following link (https://bio-medical.com/disposable-webbs-silver-silver-chloride-electrodes-10-pack.html) seem appropriate as the Grass paste applied to the lightweight webbed electrodes may be visually monitored as it gradually disappeared. I would, however, need to employ nurses with the physician's permission to add paste as and when required during the 9 to 12 hour collection of EEG data. I quote the relevant part of the product description in the link: "Disposable Webbed EEG Electrodes are designed to increase patient comfort while providing quality recordings that can last through both night and day studies and for multiple days." The ten million dollar question is whether these electrodes are compatible, or can be used, with the OpenBCI headband. The answer would seem to me to be 'no', because the Velcro headband would tend to hide or smother the webbed electrodes. And while the Ultracortex IV headset may seem better suited to house the webbed electrodes, it could clearly not be worn for long by a patient in the reclining position. So, if neither the headband nor Ultracortex IV headset could provide suitable support or housing for the webbed electrodes, are they (the webbed electrodes) meant to adhere on their own, with the applied paste, to the skin of the forehead and scalp (through the hair on head)?
Perhaps, I have overlooked something here and should really be asking the following question:-
Could the webbed electrodes in the link provided above be attached through the holes of the OpenBCI headband and fed with Grass paste using a syringe while in position without the headband being removed?
I suggest just using the plain cup electrodes, silver chloride, that I mentioned previously. These are what are used in PSG clinics. Not the webbed type. You want to discourage evaporation by having the electrode enclose the paste. Then additional EC3 / gauze layer on top, with a flexible wrap over all. As mentioned in the previous pdf. I'm trying to get a copy of the paper from the authors,
https://www.ncbi.nlm.nih.gov/pubmed/15982926
Will post on this thread if they reply.
All electrode types are compatible with OpenBCI. Paste and gel electrodes do NOT need headbands. Instead follow the suggestions in the paper / pdf already posted. Ultracortex can not be used for sleep EEG. View some tutorial videos on EEG cup electrode placement. The paste holds them in place, and the additional gauze layer with EC3 will block evaporation. The overwrap semi-elastic head bandage then prevents gross movement of the electrode leads or tugging on the electrodes.
No, just follow the procedure being used by the pdf, paper, and @Frederik_D_Weber .
The overwrap layer in the pdf is likely,
https://www.amazon.com/Self-Adherent-Cohesive-Self-Adhesive-California-Basics/dp/B0711MDC8N/
4-inch Wide Self Adherent Cohesive Wrap Bandages (8 Pack) Bundle, 5 yds Self Adhesive Non Woven Bandage Rolls, Brown Athletic Tape for Wrist, Ankle, Hand, Leg, Premium-Grade Medical Stretch Wrap
hereby confirm 12-14 hours definitly OK, do not know of any better paste for single electrode (without electrode cap) attachement over long periods (that you can also remove easily later on), if you use a little medical tape to cover the electrode, this is even better (keeps it a bit moist as to not dry out).
@wjcroft @Frederik_D_Weber Thanks Vielen Dank. However, without the OpenBCI Headband Kit or Ultracortex Mark IV EEG Headset, it would take practice to get the positioning of the electrodes correct. How does a novice achieve this (International 10-20 system) using a tape measure and marker given that head sizes differ from person to person?
http://openbci.com/forum/index.php?p=/discussion/176/placing-electrode-sensors-on-the-scalp
https://bio-medical.com/brainet-placement-caps.html
@wjcroft Having looked at
http://openbci.com/forum/index.php?p=/discussion/176/placing-electrode-sensors-on-the-scalp
and
https://bio-medical.com/brainet-placement-caps.html
the following question arises:-
Can placement caps be used in combination with disposable electrode cups, EC2/EC3 cream and an overwrap bandage to keep the electrode cups + EC2/EC3 paste + gauze in place? If they can be used in combination with one another, is there anybody in the forum that has direct experience of this combination which to me would appear to amount to wearing some kind of lightweight motorcycle crash helmet (although said to be easily removable with a damp, warm towel)?
One alternative would be to use the Brainet placement guide just temporarily, and some type of washable skin marker pen to place a dot slightly to one side of each site. Then remove Brainet.
I don't understand your reference to the "motorcycle crash helmet" idea. The technique described earlier in the pdf attachment, is not bulky. The idea is to just use the EC3 and keep it from evaporating overnight.
@wjcroft Firstly, "The spikey electrodes are particularly difficult to insert ...:" This is obviously quoted from OpenBCI documentation on the headband kit. Could you tell me whether the newly introduced Dryodes (https://shop.openbci.com/products/idun-dryode-kit?variant=31081774874696) can serve the same function as spikey electrodes? Or do they only serve the same function as EMG, ECG and flat EEG Snap Electrodes?
Secondly, Does the term "spikey electrodes" include the 5mm comb electrodes and, if so, are the 5mm comb electrodes equally difficult to insert?
Thirdly, once bought, it would remain to be seen whether the Dryodes live up to the claims made for it ("research-grade signal quality" and "Impedance range is 3.2-5.2 kOhm, unprecedented for dry electrodes")..
Fourthly, my hunch is that the IDryodes of the DUN Dryode™ Kit are supposed to be used independently with their adhesive patches as their only support/scaffolding meaning that they cannot be used in combination with the headband kit. Is this correct?
Hi, Scipio, we did cover the idea that most sleep studies use the previously mentioned cup electrodes with paste (EC3) and a cover layer to prevent evaporation. This seems to be the most widely used procedure for clinical sleep EEG / PSG. The skin / electrolyte boundary, because it is liquid, offers the best and most stabile impedance connection. Particularly since in a sleep study, the head is moving around on the pillow overnight. This puts differing amounts of pressure on various electrodes over the course of the recording.
I would not recommend the dry electrodes for the previously mentioned reasons. To address your particular question, "...difficult to insert...", just means a small amount of finger pressure is needed, as shown in the pictures. The flat dry electrodes go into different 'snap' connectors, so are easier to insert. The Dryode electrodes use the same snap connector. Note however that the Dryodes were mostly designed for bare skin application areas. I am not clear how they perform with dense hair. Might depend on how dense / thick is the hair in that area. Obviously the Dryode needs some external means to hold it in place. So any type of strap or adhesive can work, including the velcro.
@wjcroft In the following link below, silver cup electrodes are more expensive than gold cup ones. Is the reason for this that the silver cups are more durable, conduct better or are, simply, more expensive to manufacture?
https://www.cnsac-medshop.com/product-category/electrodes/cup-electrodes/
Silver and tin cup electrodes are solid, usually cast, silver and tin. Whereas all gold cups are likely stamped tin with gold plating. Solid silver or tin electrodes last indefinitely with care. Gold cups, if the plating is chipped or damaged, will distort badly due to galvanic battery effects.
However, I believe a trend in clinical environments, hospitals, etc., is to use 'disposable' electrodes that are likely plastic, then silver plated, then chlorided. Ag-AgCl electrodes have the most superior signal stability and lack of distortion. And even though they are 'disposable', could generally be used multiple times if carefully washed. Most of the FRI electrodes are silver chloride.
@wjcroft Do you know whether these CNSAC electrodes are compatible with the Cyton board or would they need adapter's?
Or does what you said previously in the following context (and I quote you) apply?
ALL common EEG and ECG electrodes use the touchproof connectors. You can see that in the CNSAC photos.
@wjcroft I am convinced that the CNSAC Easy Head (https://www.cnsac-medshop.com/product/easy-head-size-m/) can be worn throughout a sleep study session of many hours having been appropriately marked with the help of markers (https://www.cnsac-medshop.com/product/eeg-markers-in-various-colors/), the Brainet placement cap (https://bio-medical.com/brainet-placement-caps.html) and suitably prepared with Nuprep (https://www.cnsac-medshop.com/product-category/pastes-gels/skin-preparation/), gauze swabs (https://www.cnsac-medshop.com/product/gauze-swabs-for-eeg-psg-4-ply-non-sterile-400-pcs/), band (https://www.cnsac-medshop.com/product/fixomull-stretch-klebevlies10-m-x-5-cm/) and, of course, EC2 conductive paste (https://www.cnsac-medshop.com/product/ec2-adhesive-electrode-cream-10-tubes-x-100g-kopie/). Your additional comments on this would, as usual, be highly appreciated, although I am aware we have covered much of this in comments above.
Did you see the long-term EEG monitoring Caps from Greentek sensors?
http://www.greenteksensor.com/eeg-caps/sleep-eeg-caps/
Bennie Dengs instruction from Greentek sensors how to use this cap is really impressive. He looks as if it was hard work to get this solution.